Administering an injection is a process which presents a number of risks and challenges for users and healthcare professionals, both mental and physical.
Injection devices (i.e. devices capable of delivering medicaments from a medication container) typically fall into two categories—manual devices and auto-injectors.
In a manual device—the user must provide the mechanical energy to drive the fluid through the needle. This is typically done by some form of button/plunger that has to be continuously pressed by the user during the injection. There are numerous disadvantages for the user from this approach. If the user stops pressing the button/plunger, then the injection will also stop. This means that the user can deliver an underdose if the device is not used properly (i.e. the plunger is not fully pressed to its end position). Injection forces may be too high for the user, in particular if the patient is elderly or has dexterity problems.
The extension of the button/plunger may be too great. Thus it can be inconvenient for the user to reach a fully extended button. The combination of injection force and button extension can cause trembling/shaking of the hand which in turn increases discomfort as the inserted needle moves.
Auto-injector devices aim to make self-administration of injected therapies easier for patients. Current therapies delivered by means of self-administered injections include drugs for diabetes (both insulin and newer GLP-1 class drugs), migraine, hormone therapies, anticoagulants etc.
Auto-injectors are devices which completely or partially replace activities involved in parenteral drug delivery from standard syringes. These activities may include removal of a protective syringe cap, insertion of a needle into a patient's skin, injection of the medicament, removal of the needle, shielding of the needle and preventing reuse of the device. This overcomes many of the disadvantages of manual devices. Forces required of the user/button extension, hand-shaking and the likelihood of delivering an incomplete dose are reduced. Triggering may be performed by numerous means, for example a trigger button or the action of the needle reaching its injection depth. In some devices the energy to deliver the fluid is provided by a spring.
Auto-injectors may be disposable or single use devices which may only be used to deliver one dose of medicament and which have to be disposed of after use. Other types of auto-injectors may be reusable. Usually they are arranged to allow a user to load and unload a standard syringe. The reusable auto-injector may be used to perform multiple parenteral drug deliveries, whereas the syringe is disposed after having been spent and unloaded from the auto-injector. The syringe may be packaged with additional parts to provide additional functionality.
US 2002/0095120 A1 discloses an automatic injection device which automatically injects a pre-measured quantity of fluid medicine when a tension spring is released. The tension spring moves an ampoule and the injection needle from a storage position to a deployed position when it is released. The content of the ampoule is thereafter expelled by the tension spring forcing a piston forward inside the ampoule. After the fluid medicine has been injected, energy stored in the tension spring is released and the injection needle is automatically retracted back to its original storage position.
When an auto-injector is driven by a spring, the spring force is usually highest at the beginning of the motion. With increasing extension of the spring the spring force decays. This may lead to variation in the delivery of the dose over the injection cycle.
WO 2004/107975 A2 discloses a device for fluid delivery. The device comprises a cartridge having a plurality of cavities and a plurality of penetrating members. The plurality of penetrating members are each at least partially contained in cavities of the cartridge wherein the penetrating members are slidably movable to extend outward from openings on said cartridge to penetrate tissue. Each of the penetrating members comprises a needle with a lumen coupled to a canister containing a material to be injected.
WO 01/89613 A1 discloses an injector device for delivery of liquid from a high pressure, the device comprising a housing, a pressure chamber comprising a pressure barrel for accommodation of at least one piston therein and having a front end opening for ejection of the liquid, the pressure chamber being of sufficient strength to sustain the liquid pressure. The device further comprises a storage chamber, separate from the pressure chamber, for the liquid or the liquid precursor components, and a conduit between the pressure chamber and the storage chamber. A pressurizing mechanism in the housing is arranged to apply force, directly or indirectly, on the piston in the pressure barrel to create said liquid pressure. The pressure chamber, the piston and at least a part of the conduit is arranged as a unit, wherein said unit and the housing have corresponding fitting parts allowing releasable attachment of the unit to the housing in a position permitting fluid connection between storage chamber and pressure chamber through the conduit and permitting the pressurizing mechanism to act on the piston.
WO 2007/002052 A2 discloses a method and apparatus for administering a pharmaceutical. The method employs a delivery device including a housing, a pharmaceutical containing needled syringe movable within the housing, an activation button disposed at one of the housing, and wherein the housing is flared radially outward at the other end and designed to allow visibility of the needled syringe. A skin-contacting surface of the housing at the flared end is designed to limit slippage along the skin, and at least one injection targeting guide is provided. When the device is sited for injection, and without pressing the delivery device housing toward the injection site with any predetermined force by the one hand holding the housing, the activation button may be plunged with the other hand toward the housing to trigger an advancing assembly within the device that first automatically advances the needled syringe to insert a needle into the injection site, and that second automatically advances the syringe piston to force pharmaceutical through the inserted needle.
WO 2008/112472 A2 discloses a delay mechanism for staging the operation of an automatic injection apparatus to ensure medication contents are properly delivered prior to the needled syringe of the apparatus being retracted. In one form, the delay mechanism includes a shuttle, a follower, a locking member, a damping compound, and a driver and a driver biasing element. The shuttle is for a needled syringe of the apparatus and includes a first latching element. The follower includes a second latching element and a cammable surface, which second latching element is for cooperating with the first latching element to limit motion of the shuttle relative to the follower in a second direction opposite the first direction. The locking member is movable from a locking position to a release position by engagement with the syringe plunger during an injection, the locking member, when in the locking position, preventing rotation of the follower relative to the shuttle, the locking member, when in the release position, allowing rotation of the follower relative to the shuttle. The damping compound is between the follower and a supporting surface to dampen rotation of the follower relative to the shuttle. The driver is rotatably fixed relative to the shuttle and includes a camming surface. The driver biasing element is for forcing the driver from a first position to a second position when the locking member moves to the release position, whereby during movement of the driver to the second position, the driver camming surface engages the follower cammable surface to force the follower to rotate relative to the shuttle from a latching position, at which the first and second latching elements cooperate, to an unlatching position, at which the second latching element is disengaged from the first latching element to allow movement of the shuttle for retracting the syringe needle into the housing of the automatic injection apparatus after injection.
U.S. Pat. No. 5,318,584 A discloses a blood lancet device for withdrawing blood for diagnostic purposes, in which with the aid of a lancet drive in a housing a lancet holder with a lancet positioned in it and moveable along a predetermined, straight puncture path is moved until the tip of the lancet emerges from the outlet, in order to produce a wound in a body part adjoining the outlet. The lancet holder also serves to retract the lancet into a position in which the tip is again positioned within the housing. In order to make possible a puncture involving especially little pain, the lancet drive has a rotary/sliding transmission system whose input side is formed by a transmission member which is rotatable about an axis of rotation parallel to the predetermined puncture path. This input-side transmission member of the rotary/sliding transmission system is coupled with the elastic drive element of the lancet drive and converts a torque transmitted to the transmission member into a longitudinal displacement in the direction of the predetermined puncture path, which is transmitted to the lancet holder.